Cold rolling mills



Feb. 10, 1959 G. w. LORD 2,872,833

COLD ROLLING MILLS Filed Jan. 1o. 1955 l /a I /zf 4 /5//1/8 5 y @LA Fa., o

INVEN-rolz GEORGE W- LORD Avvoanvavs United -States Patent O 'COLD ROLLING MILLS George William Lord, Wembley, England, assignor to National Research Development Corporation, London, England, a statutory corporation Application January 10, 1955, Serial No. 480,856

Claims priority, application Great Britain January 14, 1954 4 Claims. (Cl. Sil-38) This invention relates to cold rolling mills and has particular reference to mills for cold rolling metal sheet especially metal strip.

It is known that small diameter rolls will give a greater reduction in thickness whenrolling metal strip than large diameter rolls but it is found that small diameter rolls tend to become distorted when a load is applied `to them. Distortion is normally prevented by providing large diameter rolls, known as backing rolls, to support the small diameter rolls, referred to as vwork rolls. The backing rolls Vcan be effectively loaded and in turn apply the load to the work rolls which may themselves be driven directly while the backing rolls may rotate freely. Alternatively the backing rolls may be driven and the work rolls driven by frictional `engagement with the backing rolls. In spite of the support provided by the backing rolls it is kfound that there is some distortion of 4the work rolls during rolling which increases as the diameter of the work rolls, for a given length, is reduced. Thus, a lower limit is set on the thinness of strip which may be produced.

It is an object of the present invention to provide an improved cold rolling mill capable of producing thinner strip than known mills.

According to the present invention a cold rolling mill comprises two work rolls each having a backing roll, the arrangement of the work rolls being such that the plane containing their axes is inclined to the plane containingr the axes of the backing rolls, means being provided for supporting each work roll along its length intermediate its lines of contact with its supporting roll and the other work roll to prevent distortion of the work roll during rolling.

Preferably the line of contact between the work rolls lies in the plane containing the axes of the backing rolls. The angle between the plane containing the axes of the work rolls and that containing the axes of backing rolls advantageously lies Within the range of 20 to 30.

The invention is particularly applicable when the diameter of the work rolls is less than about one sixth of their length or when the diameter is less than 1 inch, irrespective of length.

In one embodiment of the invention the means for supporting the work rolls comprises bearing blocks rigidly mounted in a framework placed between the backing rolls.

As an example only, one embodiment of the invention for cold rolling metal strip will now` be described in greater detail with reference `to the accompanying drawings of which Fig. l is a vertical cross section of part of the mill, and

Fig. 2 is a perspective view of a work roll supporting framework.

The general construction of the rolling mill is similar to that of known mills and it comprises two backing rolls 1, 2 of large diameter rotatably mounted in a rigid frame and driven from an electrical motor through the usual reducing gear and coupling, none of which are shown in 2,872,833 ce Patented Febrlo, 1959 the drawing. Screw operated pressure means (not shown) are tted at the top of the frame to apply .a required load to the backing rolls during rolling. The backing rolls 1, 2 support small diameter work rolls 3, 4.

Positioned between the backing rolls is a framework comprising two tie-bars 5, 6 spaced apart and secured at one end to a bracket 7 which engages the end of the table of the mill and is bolted thereto. The tie-bars are formed to receive two pressure plates 8, 9 each mounted between two recesses in the tie-bars. The opposed faces 10, 11 of the pressure plates are concave and receive the convex faces 12, 13 of bearing blocks 14, 15. The bearing blocks taper from the convex faces towards faces which are formed to receive bearing pads 16, 17 of phosphor bronze or other suitable material. The work rolls are maintained in contact with the bearing pads. The ends of the work rolls are prevented from scoring the tie-bar surfaces by blocks or pads 21 of, for example, hardened tool steel or phosphor bronze mounted in suitable recesses in the tie-bars. The pads 21 serve also to prevent endwise movement of the work rolls 3, 4.

Each pressure plate is drilled as at 1 8, and a lubricant feed pipe 19 is passed therethrough and communicates with a passage 20 formed in the adjacent bearing block and its bearing pad.

Before operation of the mill, the work rolls are dropped into the space between the bearing blocks care being taken to ensure that the rolls seat correctly. The length of the work rolls will, in general, be determined by the width of the strip to be rolled and the diameter of t the rolls will be determined by the final thickness of the product. For example, with work rolls of 1 inch diameter, a reduction of thickness from 0.016 inch to about 0.0016 inch can be obtained. Work rolls of 1/2 inch diamter are satisfactory for reducing strip from 0.004 inch-0.0008 inch; rolls of 1A inch diameter will effect a reduction in thickness from 0.002 inch-0.0004 inch, whilst Ms inch diameter work rolls will reduce strip of 0.001 inch thickness to a linal thickness 0.00015 inch. Reductions of' about 50% per pass, starting with annealed strip on nickel iron alloys, are possible using the roll sizes stated.

The space between the bearing blocks is suicient to allow the work rolls to seat in staggered fashion so that a plane taken through the axes of those rolls is inclined to a vertical planetaken through the axes of the backing rolls. The angle between the two planes may conveniently lie within the range of 20 to 30 but other values may be satisfactory provided that the angle is not small enough to allow the lower work roll to be drawn past the upper work roll during rolling, nor large enough for the friction between the bearing pads and the work rolls to exceed the friction between the latter and the backing rolls. The line of contact between the work rolls preferably lies in the vertical plane containing the axes of the backing rolls.

The end of the strip to be rolled is next placed between the Work rolls and the upper backing roll is brought down bythe screw operated pressure means to a desired setting. Rolling can then be -commenced using the conventional tensioning and coiling devices. During rolling, equal back and forward tensions of between 50-80% of the breaking load of the emerging rolled strip are applied to the strip.

Precautions must also be taken to ensure that the work roll surfaces and the strip surfaces are kept clean. In particular, some form of dust proofing is desirable since the presence of dust on the rolls or strip may result in perforations in the finer gauge strip. The mill may be installed in an air conditioned room and shields may be fitted to reduce the likelihood of dust settling on the strip or the rolls.

There is considerable initial Wear on the phosphor bronzebearing pads but a bearing area is soon formed after which the pads wear at a slow rate. Wear on the pads, provided it is even, is of little importance and results only in an increase in the angle between the two planes referred to above and a slightly altered upper backing roll adjustment.

It will be understood that the line of contact of the work rolls tends to remain in the plane containing the axes of the backing rolls even though wear takes place at the bearing pads. A cold rollingA mill according to the invention also permits the use of work rolls of a smaller diameter than hitherto thus enabling thinner strip to be rolled.

The workI rolls are not mounted in the usual bearings but are free and float between the backingV rolls, endwise movement of the workrolls being prevented by the pads 21.

It will be appreciated that each work roll is supportedby its backing roll, the other work roll and the bearing block along lines of Contact spaced around the periphery of the work roll. This spaced support prevents distortion of the work roll during rolling enabling a greater reduction to be eiected than hitherto. Variations in the thickness of the rolled strip are also very much less than with known mills.

I claim:

1. A reversible four high cold rolling mill comprising in combination two backing rolls, means for supporting said backing rolls with their axes in spaced parallel relationship in the same plane, rst and second work rolls, and a single unitaryv framework supporting both of said work rolls between saidbacking rolls with the axes ofthe work rolls being positioned parallel to those of the backingl rolls in a plane intersecting said plane of said` backing roll axes at an acute angle, the two work roll axes lying on opposite sides of the plane of said backing roll axes and the line of contact between said work rolls lying within said last mentioned plane, said framework being positioned symmetrically with respect to said line of contact and comprising two end members which run parallel to the axes of the rolls and transverse tie bars rigidly connecting said end members, said end members being provided with bearing means extending along the inner sides thereof parallel to said work rolls, said bearing means and tie bars defining arecess dimensioned to receive said work rolls, and said end members laterally supportingl through saidI bearing means eachv of said Work rolls on the side Ifurthest' from the plane of said backing roll axes. Y

2. A four high cold rolling mill as claimed in claim 1 in which said framework is detachable as a unit from the remainder of the mill.

3. A four high rolling mill as claimed in claim l in which the angle between the plane of said backing roll' axes and that of said working roll axes is between twenty and thirty degrees.

4. A four high cold rolling mill as claimed in claim 1 in which vsaid bearing means are blocks, each having a concave surface dimensioned to receive one of said workrolls.

References Cited in the le of this patent UNITED STATES PATENTS 1,466,459 Perry Aug. 28, 1923 1,813,129 White Julyv 7, 1931 1,887,870 Coe Nov. .15, 1932 FOREIGN PATENTS 368,679 Great Britain Mar.- 10, 1932 

